Re: [Qemu-devel] [PATCH v6 16/25] block: Add 'base-directory' BDS option

[Kevin Wolf]

Am 07.11.2017 um 13:07 hat Alberto Garcia geschrieben:
> On Thu 02 Nov 2017 11:06:28 PM CET, Eric Blake wrote:
> 
> >>>> Using this option, one can directly override what bdrv_dirname()
> >>>> will return. This is useful if one uses e.g. qcow2 on top of quorum
> >>>> (with only protocol BDSs under the quorum BDS) and wants to be able
> >>>> to use relative backing filenames.
> >>>>
> >>>> Signed-off-by: Max Reitz <address@hidden>
> >>>
> >>> Who would be using this option in practice? I understand that
> >>>management tools should be using always absolute filenames, and this
> >>>API doesn't seem so convenient for humans.
> >> 
> >> Hmmm.  I seem to recall Eric liked it a couple of years ago when he
> >> was still more on the libvirt side of things. :-)
> >
> > Ideally, libvirt should be using node names rather than filenames
> > (whether absolute or relative); but I still think it could be
> > something that turns out to be useful.
> 
> But what would be the use case? For a management tool it's not more
> convenient to use relative file names, or is it?

If we add an external API, we must maintain compatibility in future
versions, so taking the patch comes with a cost. So I agree with you
that we better wait for an actual use case rather than just "could turn
out to be useful to someone maybe".

(Also, so that I don't have to post a second reply to a patch that might
be dropped: "Since: 2.10" wouldn't be quite right any more either way.)

Kevin